"We wanted to ensure that no one missed what the Romney campaign believes is a critical moment in the campaign for them," a top Obama campaign official tells ABC News.

(The Obama campaign points out that technically only tweets signed "-BO" can be officially considered personally from President Obama, even if the official twitter account is from "@BarackObama.")

Just minutes before, Teddy Goff, the digital director of Obama for America, had started re-tweeting previous Trump messages, such as "When will @BarackObama release his transcripts? What is he hiding?"

As ABC News political director Amy Walter reminds usaccording to a Fox News poll taken last month, Americans were nearly three times as likely to say they'd be less apt rather than more apt to vote for a candidate Trump endorsed, 27 percent to 10 percent. Two-thirds said it would make no difference.

Democrats also feel Romney appearing with Trump at the event demeans him.